Method of applying metal filaments to surfaces

ABSTRACT

Method of applying metal filaments to a surface comprises forming a network composed of metal filaments entwined with nonconducting thermoplastic filaments, stabilizing the network by bonding the filaments at their junctions to form a selfsupporting element and fusing the element as a whole with a plastic sheet which is then applied to a surface.

United States Patent Breitner June 10, 1975 METHOD OF APPLYING METAL[56] References Cited FILAMENTS T9 SURFACES UNITED STATES PATENTS [76]Inventor: Wilhelm Breitner, Bopser-strasse 2,439,892 4/1968 l-luck 219529 Stuttgart, Germany 3,472,289 10/1969 Webber et a1 66/202 I 3,484,58412/1969 Shaw, Jr. 219/203 [221 Flled- 1973 3,506,526 4/1969 Toyooka161/93 [21] Appl. No.: 392,247

Primary Examiner-George F. Lesmes Related Apphcauon Data AssistantExaminerS. S. Silverman [63] Continuation of Ser. No. 154,586, June 18,1971,

abandoned.

[57] ABSTRACT [30] Foreign Application Priority Data Method of applyingmetal filaments to a surface com- June 19, 1970 Germany 2030204 prisforming a network composed of metal filaments entwined withnon-conducting thermoplastic fila- [52] US. Cl. 156/93; 156/106;156/148; ments, stabilizing the network by bonding the fila- 156/177;156/179; 161/5; 161/50; 161/89; ments at their junctions to form aself-supporting ele- 161/91; 161/92; 161/93; 161/170; 219/203; ment andfusing the element as a whole with a plastic 219/529; 264/104 sheetwhich is then applied to a surface. [51] Int. Cl B32b 17/04; B32b 17/10[58] Field of Search 264/104; 161/DlG. 4, 88,

9 Claims, 5 Drawing Figures 1 METHOD OF APPLYING METAL FILAMENTS TOSURFACES This application is a continuation of my copending applicationSer. No. 154,586, filed June 18, 1971 now abandoned.

The present invention relates to a method for applying metal filaments,metal wires or the like to surfaces.

Laminated glass panels are known which comprise two sheets of glass andan intermediate layer of a sheet material such as polyvinyl butyral,PVC, polyethylene, etc., in which the sheet material contains a systemof electric conductors, in form of thin metal filaments.

This type of panel is used for heated windows for automobiles, aircraft,apartments, deep-freezing chests or the like, to prevent the formationof ice or frost. Another application of panels of this type are theso-called alarm glasses, which are used for panelling shop windows, showcases or the like. When the glass is broken, for instance in case of aburglary, the current-carrying thin metal wire is cut, thus interruptingthe electric circuit in order to start an alarm signal. Finally, it isalso possible to arrange electric conductor systems in or on glasses orother surfaces to provide electric shielding, or else to be used asreceiving or sending antennas. The invention to be subsequentlydescribed relates to all of the above-mentioned embodiments andapplications of electric conductor systems arranged in or on a surface.The known methods for embedding or applying thin wires onto flat,particularly transparent, bodies have proven to be complicated, laborconsuming and, consequently, expensive. A known method of this typeconsists in rolling wires, stretched in straight lines or laid out inwavy form, into a plastic sheet. Hitherto known methods only permittedthe use of wave forms of the type of the so-called sine wave form,which, however, are so familiar to the human eye that the eye isinvoluntarily distracted and hampered while looking through the glass.

Therefore, one object of the invention is to apply electric conductorsystems to surface-bodies in a simpler way than by means of the heretoknown methods, particularly in such a manner that essentially anydesired configurations of the single current conductors can beaccomplished. The invention preferably relates to the manufacture ofheated glass sheets.

Another object of the invention is to mechanically prefabricate theheating conductor system as an independent structure, or element, withthe purpose of permitting economical large-scale production, andparticularly in such a manner that the prefabricated heating conductorsystem canbe embedded without excessive manual labor as a separate layerin a glass-plastic laminated structure, or can be inserted into theplastic sheet during the sheet manufacture, or be applied to any othersurface, for example a plate, by means of an adhesive.

To realize these objects, the method according to the inventioncomprises the steps of combining flexible electric conductors, such asmetal filaments, with an electrically insulating support structure toform a surface-element, and applying this element is form of a layer tothe surface, whereby the support structure preferably comprisesfilaments made of insulating material which is intermingled, knitted,stitched, stapled or otherwise entwined with the metal filaments to formthe surface-element.

Preferably, the metal filaments are'connected with main conductors atthe edges of the surface-element, which can be accomplished by knitting,entwining, twisting or the like.

When manufacturing a heating conductor system which is arranged betweentwo glass sheets it is convenient that a support structure, such as anetwork, consisting of thermoplastic filaments be embedded by fusion ina thermoplastic sheet, together with the simultaneously knitted metalfilaments, and that this plastic sheet be integrelly fixed to a glasssheet.

Further features, advantages and applications of the invention will beapparent from the following description in connection with theaccompanying drawings, in which:

FIG. 1 shows a network, according to the invention, made of metalfilaments and electrically insulating filaments, and a plastic sheet, towhich it is to be attached;

FIG. 2 shows the network of FIG. 1 fused into the plastic sheet;

FIG. 3 shows a sheet of laminated glass, combined with the fused sheetof FIG. 2;

FIG. 4 shows a plastic sheet provided with a heating conductor systemstitched on it according to the invention; and

FIG. 5 shows a schematic view of the stitching technique used during themanufacture of the sheet of FIG. 4.

A network I, having a so-called rib stitch is shown in the upper portionof FIG. 1 and comprises electrically insulating transparentthermoplastic and preferably fusible plastic filaments 2 intertwinedwith electrically conducting metal wires or metal filaments 3. Thefilaments 2 may also be provided with a core made of metal or of anotherinorganic material which is coated with a transparent fusible andinsulating substance. The metal filaments 3 are generally connected, atthe ends of each row, with main conductor wires 4 which are used tosupply the current. The network I is preferably stabilized in itssurface-configuration, for example by bonding the connecting portions ofthe loops by means of a slight fusion, so that the wave form of thesingle metal filaments 3 will be retained.

Network 1 is applied to a sheet 5 of preferably the same transparentthermoplastic material as the filaments 2 such as polyvinyl butyral, PVCor polyethylene.

After placing the network 1 onto sheet 5 the filaments 2 of the networkare fused (or bonded) with the sheet 5, so that they become invisible.Simultaneously, the metal filaments 3 are combined with sheet 5 as isshown in FIG. 2. The fusion of the network with sheet 5 can beaccomplished, for example, by means of heated rolls, whereby the networkand the sheet are fed under pressure between two of such rolls.Optionally, a cover sheet can be laid on top of the network before theoperation of hot rolling. The bottom sheet, the

cover sheet, and the network arranged between them result in a solidlaminated structure.

The transparent sheet 5, shown in FIG. 2, including the metal filaments3 embedded in their predetermined and stabilized wave form, can beapplied to the front or rear surface of a pane of glass of anautomobile, provided it is appropriately shaped to fit. By connectingthe main conductors 4 with a current source, the sheet and the pane maybe heated, thus preventing the formation of frost or ice.

FIG. 3 shows a heatable sheet of laminated glass manufactured by usingthe element shown in FIG. 2. The sheet 5, containing the metal filaments3, is inserted between two glass sheets 6, such as prestressed glass(so-called safety glass). By heating and slightly melting the surface ofsheet 5, and under simultaneous compression, a solid bond is achievedbetween sheet and the glass sheets 6. If the main conductors 4 areconnected to a current source, the sheet of laminated glass, accordingto FIG. 3, can be heated.

Usually, the front and rear panes of automobiles are shaped into specialcharacteristic forms and curvatures. The network I and the sheet 5. canbe shaped during its initial stages of manufacture so that it will matchwith the form of the corresponding pane of the automobile, whereby thepreviously mentioned stabilization of the network 1 will maintain thedesired form. This matching of the form of the network 1 with the paneto be heated represents a considerable advantage over known methods.Another advantageous feature consists in that, according to theinvention, any kind of desired wave form of the metal filaments 3 can bechosen. This can easily be achieved by selecting corresponding textilestitches. Such stitches can be, for example, the tuck stitch or theopenlap. The resulting configurations of the filament arrangement areless familiar to the eye, so that the view through glass sheets providedwith such structures is not obscured.

FIGS. 4 and 5 illustrate a modified form of the invention in which themetal filaments 13 are directly stitched on a transparent thermoplasticplastic-sheet which corresponds to sheet 5 in FIGS. 1-3. Instead ofstitching the filaments on the sheet, they can also be stapled orcrocheted thereto. The sheet 15 may also be perforated beforehand at thestitching locations. In addition, the sheet 15 may also be replaced by afabric, wither woven, knitted or randomly formed of transparentthermoplastic filamentary material. FIG. 5 shows that during theoperation of stitching or crocheting the electrically conducting metalfilament 13 may be used as the bottom thread, while the upper thread 12consists of a transparent thermoplastic material or glass, which issubsequently fused or bonded to the sheet by heat. Alternatively, theupper thread can be the metal filament and the bottom thread plasticfilament. In addition, the metal filaments can be coated withthermoplastic material. Finally, metal filaments coated with plastic canbe used as upper and bottom threads.

The application of heat at the same time causes fusion of the metalfilament 13 into the sheet 15. In the same manner as in FIGS. 1-3, thesingle metal filaments 13 are again connected at the edges of sheet 15with main conductors 14 which supply the current. The further processingof the sheet 15 which is provided with the metal filaments 13 isanalogous to the abovedescribed processing of the sheet 5 provided withthe wires 3.

The gage of the metal filaments 3 or 13, used according to theinvention, depends upon the amount of electric current which will flowthrough the metal filaments. If for this reason or due to a decrease invisibility it is necessary to use especially fine wires, eitherpartially or wholly, which might break, during the operations ofknitting, sewing, connecting netting, etc., it is possible to coat thethin metal filaments with an insulating plastic jacket, which is astransparent as possible, or with a glass coating (glass filaments, orglass film),

which later will invisibly fuse or combine with the material of eithersheet 5 or 15. Preferably, the coating of the metal filaments shouldhave the same index of refraction as the surrounding material of thesheet or of the plate. The coating may also consist of the same materialas the sheets 5 or 15.

If the electric conductor system which is to be applied to the surfaceof a body solely to provide heat. or to serve for shielding electricfields, the network 1 may be manufactured entirely of metal filaments,which can be combined in any desired manner to be subsequently fusedinto a plastic sheet.

A further advantage of the invention resides in the fact that, byselecting corresponding wave forms, patterns may be produced which canbe exactly adapted to the conditions of each case, with respect to theelectric heating capacity to be achieved, because a practicallyunlimited variation in the wire length per course is possible. In thepresently known art of manufacturing heating panels, the lack of such anadditional variable represents a considerable drawback which results inthe fact that not every desired shape can be produced which will alsoproduce the desired heating capacity. In addition, according to theinvention, it is possible to arrange the metal filaments in a closermanner than heretofore, so that a more concentrated conductorarrangement per unit of surface area can be obtained. Again, thisresults in the advantage of a smaller specific heat energy per conductorin the heating panel.

The network 1, shown in FIG. 1, or the like, used according to theinvention, can be economically manufactured, in any desired width, onmachines which are known and which permit the desired form and size ofthe stitches to be achieved. The network or the like can be rolled upfor transport to the site of processing, in which case a paper sheet canbe used as a temporary protective separator layer. The stabilization ofthe network, which is preferably accomplished before being rolled up,may be simply achieved by a short heating process during which theplastic filaments 2 are fixed to the metal filaments 3 by self-bondingat the junctions of the loops. The filaments 2 can also consist ofinorganic materials. In this case, however, these filaments should beprovided with a thermoplastic coating to permit the stabilization to beaccomplished. This same effect can also be attained if the electricallyconducting metal filament is provided with a thermoplastic coating or istwisted with, or surrounded by, a plastic filament.

The metal filament 3, or 13, can also be twisted with one or morefilaments made of transparent organix or inorganic materials if themetal filaments are so thin that they cannot be mechanically processed,due to their low tensile strength. In this case the material used forthe secondary filaments is intended to increase the tensile strength.

In most cases, the electric conductor systems embedded in laminatedglasses or generally applied to surfaces are connected in parallel, inorder to accomplish the objects mentioned above. However, it is alsopossible to connect the metal filaments 3, or 13, in series, which canbe done by applying suitable knitting or entwining techniques. In casethe single metal filaments 3, or 13, are connected in parallel it isconvenient to knit, sew, entwine or set the main conductors 4, or 14, atthe lateral edges and, eventually, to conform them as marginal wire.This also represents a considerable advantage with respect toconventional methods which require the main conductor to be applied asspecial metal strips in a labor consuming process.

According to the invention, predetermined surface patterns of theconductor systems, providing variable area concentration of the metalfilaments, can be obtained by means of a programmed control of theknitting, entwining or stitching machines. These patterns can either beconnected in a series, or parallel system, or combinations of the two.

The separation between the courses of current conducting filaments 3 inFIGS. 1-3 can also be increased by interposing more than one course ofinsulating filament 2. On the other hand, two or more current conductingcourses can be arranged side-by-side, whereby one or more electricallyinsulating courses can follow a group of such conducting courses.

Additionally, a variably directioned current flow can be obtained byusing metal filaments of variable conductivity, which represents aconsiderable advantage in the form of a surface-resistance if a networkor the like is used which consists only of metal filaments. In FIG. 1the filaments 2 would consist, in this case, of a metal with a smallerconductivity than the filaments 3, resulting in a variation in theheating capacity of successive areas of the surface.

I claim:

1. A method for producing a transparent glass sheet of a predeterminedshape having an open transparent network of metallic filaments combinedtherewith, comprising the steps:

a. intertwining a plurality of metallic filaments in a transparent wavypattern with electrically insulating fusible filaments by a techniqueother than weaving;

b. connecting said metallic filaments with a main electrical conductor;

c. stabilizing the metallic and insulating filaments by joining themtogether by means of a slight fusion of the insulating filaments withthe metallic filaments at their junctions to form an open transparentstabilized self-supporting network;

d. shaping the stabilized self-supporting network to match with theshape of said glass sheet;

e. applying said network to a transparent plastic sheet and fusing thenetwork into said plastic sheet to render said insulating filamentsinvisible;

f. fastening said plastic sheet containing the fused network to thesurface of said sheet of glass.

2. The method as defined in claim 1 in which the insulating filamentsare fusible thermoplastic filaments.

3. The method as defined in claim 1 in which the insulating filamentsconsist of inorganic materials, especially glass, and are provided witha thermoplastic coatmg.

4. The method as defined in claim 1 in which the metallic filaments areprovided with a thermoplastic or glass coating.

5. The method as defined in claim 4 which includes the steps ofemploying metallic filaments having different conductivities, andarranging said filaments to define areas in the network having differingheating capacities.

6. The method as defined in claim 4 which includes the steps of knittinga course of electrically insulating filament with at least one course ofmetallic filament to form said network.

7. The method as defined in claim 4 which includes the steps ofstitching the metallic and insulating filaments to a supporting sheet toform said network.

8. The method as defined in claim 7 which includes the steps ofemploying a plastic supporting sheet and perforating said sheet atspaced intervals for said stitchmg.

9. The method as defined in claim 7 which includes the steps ofstitching the metallic filaments to a plastic sheet and applying theplastic sheet including the filaments to a surface.

1. A METHOD FOR PRODUCING A TRANSPARENT GLASS SHEET OF A PREDETERMINEDSHAPE HAVING AN OPEN TRANSPARENT NETWORK OF METALLIC FILAMENTS COMBINEDTHEREWITH, COMPRISING THE STEPS: A. INTERWINING A PLURALITY OF METALLICFILAMENTS IN A TRANSPARENT WAVY PATTERN WITH ELECTRICALLY INSULATINGFUSIBLE FILAMENTS BY A TECHNIQUE OTHER THAN WEAVING; B. CONNECTING SAIDMETALLIC FILAMENTS WITH A MAIN ELECTRICAL CONDUCTOR; C. STABLIZING THEMETALLIC AND INSULATING FILAMENTS BY JOINING THEM TOGETHER BY MEANS OF ASLIGHT FUSION OF THE INSULATING FILAMENTS WITH THE METALLIC FILAMENTS ATTHEIR JUNCTIONS TO FORM AN OPEN TRANSPARENT STABILIZED SELF-SUPPORTINGNETWORK; D. SHAPING THE STABILIZED SELF-SUPPORTING NETWORK TO MATCH WITHTHE SHAPE OF SAID GLASS SHEET;
 2. The method as defined in claim 1 inwhich the insulating filaments are fusible thermoplastic filaments. 3.The method as defined in claim 1 in which the insulating filamentsconsist of inorganic materials, especially glass, and are provided witha thermoplastic coating.
 4. The method as defined in claim 1 in whichthe metallic filaments are provided with a thermoplastic or glasscoating.
 5. The method as defined in claim 4 which includes the steps ofemploying metallic filaments having different conductivities, andarranging said filaments to define areas in the network having differingheating capacities.
 6. The method as defined in claim 4 which includesthe steps of knitting a course of electrically insulating filament withat least one course of metallic filament to form said network.
 7. Themethod as defined in claim 4 which includes the steps of stitching themetallic and insulating filaments to a supporting sheet to form saidnetwork.
 8. The method as defined in claim 7 which includes the steps ofemploying a plastic supporting sheet and perforating said sheet atspaced intervals for said stitching.
 9. The method as defined in claim 7which includes the steps of stitching the metallic filaments to aplastic sheet and applying the plastic sheet including the filaments toa surface.